1. Field of the Invention
The present invention relates to the field of liquid crystal displaying, and in particular to a direct backlight module.
2. The Related Arts
Liquid crystal display (LCD) has a variety of advantages, such as thin device body, low power consumption, and being free of radiation, and is thus widely used. Most of the LCDs that are currently available in the market are backlighting LCDs, which comprise a liquid crystal panel and a backlight module. The operation principle of the liquid crystal panel is that liquid crystal molecules are interposed between two parallel pieces of glass and a plurality of vertical and horizontal fine electrical wires is arranged between the two pieces of glass, whereby the liquid crystal molecules are controlled to change direction by application of electricity in order to refract out light emitting from the backlight module for generating images. Since the liquid crystal panel itself does not emit light, light must be provided by the backlight module in order to normally display images. Thus, the backlight module is one of the key components of an LCD. The backlight module can be classified in two types, namely side-edge backlight module and direct backlight module, according to the position where light gets incident. The side-edge backlight module comprises a backlighting source of an LED light bar arranged at an edge of a backplane that is located rearward of one side of the liquid crystal panel. The LED light bar emits light that enters a light guide plate (LGP) through a light incident face of the light guide plate and is projected out through a light emergence face of the light guide plate, after being reflected and diffused, to thereby pass through an optic film assembly to form a planar light source for the liquid crystal panel.
When compared to a liquid crystal display device incorporating a side-edge backlight module, a liquid crystal display device incorporating a direct backlight module shows advantages of high image quality (high contrast, localized light adjustment, scanning backlighting) and high energy saving. The backlight module of the liquid crystal display device evolves from the early side-edge backlight module to the direct backlight module. The conventional direct backlight module arranges a light source, such as CCFL (Cold Cathode Fluorescent Lamp) and LED (Light-Emitting Diode), at the rear side of a liquid crystal panel to form a planar light source directly supplied to the liquid crystal panel. Compared to LED, CCFL has shortcomings, such as high power consumption, high heat generation, and short lifespan and thus CCFL is gradually replaced by LED. However, a backlight module using LED as a light source has a thickness that is more than two times of that of a backlight module using CCFL as a light source, making it disadvantageous for thinning of liquid crystal display device.